Emmet strict mode move, part 2 (#37840)

Continue moving emmet extension to strict mode. This change does the following:

- Remove jsdoc types. These are unused in ts files and can easily get out of date
- Annotate when something can return undefined
- Add null checks for when something can be undefined
- Add explicit types when something can be any

extensions/emmet/src/selectItemStylesheet.ts

@@ -111,7 +111,7 @@ function getSelectionFromProperty(node: Node, document: vscode.TextDocument, sel
 		return new vscode.Selection(propertyNode.valueToken.start, propertyNode.valueToken.end);
 	}
 
-	let pos;
+	let pos: number = -1;
 	if (direction === 'prev') {
 		if (selectionStart.isEqual(propertyNode.valueToken.start)) {
 			return;